Humidifier

ABSTRACT

A humidifier for producing humidified air, particularly for use with a continuous positive air pressure device. The humidifier has an air inlet and outlet. An elongate passageway extending between the air inlet and the air outlet. The passageway is adapted to be partially filled with water so that air passing along the passageway becomes humidified as it passes over the water from the air inlet to the air outlet.

This is a continuation of application Ser. No. 08/633,413, filed Jun.10, 1996, now abandoned.

BACKGROUND

The invention relates to a humidifier for producing humidified air, andparticularly, although not exclusively, to a humidifier for use with aContinuous Positive Airway Pressure (CPAP) device.

A CPAP device is used in the treatment of obstructive sleep apneasyndrome, which is a disorder characterised by cycles of snoring,obstruction of the upper airway, and partial awakening during the night.In order to treat obstructive sleep apnea, a CPAP device can be used todeliver air under continuous positive pressure to the nasal passages ofthe patient during sleep. The positive air pressure prevents obstructionof the upper airway so that the patient is not troubled by frequentawakenings during sleep.

In order to prevent drying of the patient's airway during use of a CPAPdevice, it is known to pass the air through a humidifier beforesupplying the air to the patient. Humidification can be achieved bysimply passing the air over an area of water within a humidifier so thatthe air absorbs moisture from the water before being delivered to thepatient.

When a humidifier is used with a CPAP device, it is convenient to beable to place the CPAP device on top of the humidifier. In this case, itis desirable that the humidifier is designed so as to form a low,generally flat base for supporting the CPAP device. Such a humidifier isknown as a low-profile humidifier. Because a low-profile humidifier isof low height, it is more likely to suffer from the problem ofentrainment of water droplets in the output air flow to the patient.This problem arises because as the air passes through the humidifier itinduces waves on the surface of the water, and water droplets arestripped from the waves by the air flow, and carried by the air flow tothe outlet of the humidifier. It is also important when designing alow-profile humidifier to ensure that maximum use is made of theavailable water surface area. For example, there is no point inproviding a large surface area of water within the humidifier if the airflow passes over only a small portion of this area.

The present invention has arisen from attempts to overcome the abovedifficulties, but is not limited to low-profile humidifiers, or tohumidifiers for use with CPAP devices.

SUMMARY OF THE INVENTION

According to the invention there is provided a humidifier for producinghumidified air, comprising an air inlet for receiving air to behumidified, an air outlet for discharging humidified air, and anelongate passageway, extending between the air inlet and air outlet, fordirecting air from the air inlet to the air outlet, the passageway beingadapted to be partially filled with water so that air passing along thepassageway becomes humidified as it passes over the water from the airinlet to the air outlet.

The use of an elongate passageway between the air inlet and outletensures that the airflow passes over substantially the whole of thesurface area of the water, so that the whole of the surface area of thewater contributes towards humidifying the air flow.

Preferably, the passageway is arranged so as to direct the air from theair inlet to the air outlet along a single path.

This feature ensures that each portion of the surface area of the watercontributes equally to the humidifying of the air flow. In anarrangement where the air flow can take a number of different pathsbetween the air inlet and the air outlet, there is a danger that certainpaths will contribute more greatly to the humidifying process thanothers, for example because the air is flowing at different speeds alongdifferent paths. Such an arrangement does not make maximum use of theavailable water surface area.

In a preferred embodiment of the invention, the passageway is dividedinto a plurality of elongate subpassageways and corner portions, eachsubpassageway being substantially straight, and the subpassageways beingconnected end to end along the length of the passageway by the cornerportions.

The subpassageways can be integrally formed with the corner portions, sothat the passageway as a whole is integrally formed.

This feature avoids the possibility of leaks which might otherwise occurat the connections between the subpassageways and corner portions.

One or more of the corner portions can be generally U-shaped, so thatthe two subpassageways adjacent the or each generally U-shaped cornerportion lie side by side, and substantially parallel with each other.

For example, if the passageway is divided into two, three or foursubpassageways, the subpassageways can be arranged to form U-, S- orW-shaped serpentine passageways respectively.

It will be appreciated that the use of generally U-shaped cornerportions enables the humidifier to be of compact construction, since thesubpassageways lie side by side. This allows a greater number ofsubpassageways to be accommodated within a humidifier of a given size.

Preferably, the passageway is provided with at least one generallyU-shaped corner portion which bulges outwardly at the inside side of thecorner defined by the corner portion so as to force air passing throughthe corner portion outwardly towards the outside side of the cornerdefined by the corner portion.

This feature ensures that substantially the whole of the surface area ofthe water in the corner portion is used for humidifying the air flow.

The last corner portion through which air passes before reaching the airoutlet will be referred to below simply as "the last corner portion".

Desirably, the last corner portion, whether or not generally U-shaped,increases in width as it passes from the penultimate subpassageway tothe last passageway.

It should be understood that the word "width" used above is intended torefer to the dimension of the passageway which lies generally in theplane defined by the surface of the water, and perpendicular to thedirection of the air flow along the passageway. Furthermore, the "last"subpassageway is the last passageway through which air in the humidifierpasses before reaching the air outlet. The advantage of increasing thewidth of the passageway at the last corner portion is that it reducesthe amount of turbulence in the air flow at the corner portion. Itshould be noted that most of the air turbulence within the passageway iscreated at the corner portions, and this turbulence is particularlyacute in the case of U-shaped corner portions. The air turbulencecreates waves on the water surface which can result in entrainment ofwater droplets in the air flow at the air outlet, or, if the waves arelarge enough, indirect spillage of water into the air outlet. Byreducing the air turbulence at the last comer portion, the chances ofwater spillage, or entrainment of water droplets, at the air outlet aregreatly reduced.

Preferably, the width of the last corner portion increases gradually asthe last corner portion passes from the penultimate subpassageway to thelast subpassageway.

Such a gradual increase causes a greater reduction in air turbulence atthe corner portion.

In one embodiment of the invention, the ratio of the width of the lastcorner portion at its inlet side to its width at its outlet side is9:10.

Preferably, the upper wall, or roof, of the last subpassageway risesgradually along the length of the last subpassageway, towards the airoutlet, so as to allow the air outlet to be positioned at a greaterheight above the water within the last subpassageway.

The gradual increase in height of the roof of the last subpassagewayresults in a smooth air flow and less air turbulence.

Ideally, the roof of the last subpassageway rises gradually alongsubstantially the whole length of the last subpassageway,.

Similarly, the roof of the first subpassageway may rise gradually alongthe length of the first subpassageway, towards the air inlet, in thesame manner as the roof of the last subpassageway.

In a preferred embodiment of the invention, the passageway terminates atan end wall adjacent the air outlet, and the air outlet is arranged sothat it communicates with the interior of the passageway at a locationwhich is spaced away from said end wall.

When the air flow within the passageway creates waves on the surface ofthe water, it has been found that the water has a tendency to splashagainst the end wall of the passageway, resulting in a danger of waterspilling into the air outlet. It has been found that by spacing the airoutlet aperture away from the end wall, the danger of water spillinginto the air outlet is greatly reduced.

In a second aspect of the invention there is provided a humidifier forproducing humidified air, comprising a chamber adapted to be partiallyfilled with water, the chamber being provided with an air inlet forreceiving air to be humidified, and an air outlet for discharginghumidified air from the chamber after the air has passed over saidwater, wherein the air outlet is arranged so that it communicates withthe interior of the chamber at a location which is spaced away from allof the chamber walls.

BRIEF DESCRIPTION OF THE DRAWINGS

A preferred embodiment of the invention will now be described, by a wayof example only, with reference to the accompanying drawings, in which:

FIG. 1 is a perspective view of a W-shaped humidifier formed from atransparent material; and

FIG. 2 is a side view showing the outlet attachment of the humidifier ingreater detail.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIG. 1, the humidifier 1 comprises a W-shaped elongatepassageway 2, an air inlet 4 and an air outlet 6. The humidifier isintegrally formed by an extrusion blow-moulding process fromtranslucent, polycarbonate material. During use, the humidifier ispartially filled with water, and a use of the translucent materialenables the operator to see the water level within the passageway 2 atall times. Furthermore, the integral construction of the humidifieravoids the possibility of leaks of air and water from within thehumidifier.

The humidifier is a low-profile humidifier, and is of generally flat,rectangular, box-like construction. The upper and lower walls 8 and 10of the humidifier are pinched together along a central strip 12 and twoouter strips 14 so as to define the shape of the passageway 2. Thecentral strip 12 extends to the rear wall 16 of the humidifier, and theouter strips 14 extend to the front wall 18 of the humidifier, so as todefine a generally W-shaped passageway 2 which comprises foursubpassageways 20, 22, 24, and 26. The central strip 12 and the twoouter strips 14 also provide the humidifier with increased structuralrigidity.

The four subpassageways 20, 22, 24, and 26 are each of generallystraight, elongate construction. The first subpassageway 20 is connectedto the second subpassageway 22 by a first corner portion 28; the secondsubpassageway 22 is connected to the third (or penultimate)subpassageway 24 by a central corner portion 30; and the thirdsubpassageway 24 is connected to the fourth (or last) subpassageway 26by a last corner portion 32. All of the corner portions are generallyU-shaped, so that the four subpassageways 20, 22, 24, and 26 lie side byside and generally parallel with each other.

The central strip 12 bulges gradually as the central strip 12 passestowards the front wall 18 of the humidifier, to form an enlarged endportion 34 which defines the shape of the inside side of the centralcorner portion 30. The shape of the enlarged portion 34 ensures that airpassing through the central corner portion 30 is forced outwardlytowards the corner regions 36 of the central corner portion 30, so thatmaximum use is made of the available water surface area within thecentral corner portion 30.

The width of the last corner portion 32 increases gradually from thethird subpassageway 24 to the fourth subpassageway 26. For example, thedimensions labelled a, b and c in the drawing can be 40 mm , 45 mm, and50 mm respectively. The increase in width of the last corner portion 32reduces air turbulence within the last corner portion 32, and hencereduces the entrainment of water droplets in the air flow, and reducesspillage of water into the air outlet 6.

The roofs 38 and 40 of the first and fourth subpassageways 20 and 26respectively, rise gradually from the first and last corner portions 28and 32 to the air inlet 4 and the air outlet 6 respectively. This allowsthe air inlet 4 and the air outlet 6 to be raised in position withrespect to the second and third subpassageways 22 and 24, so thatspillage of water into the air inlet 4 or air outlet 6 is less likely tooccur. A further advantage of raising the roofs 38 and 40 with respectof the second and third subpassageways 22 and 24 is that a naturalhollow or recess 41 is formed between the first and fourthsubpassageways 20 and 26. The recess 41 is shaped so as to be ofcomplementary shape to the underside of a CPAP device so that the CPAPdevice (not shown) fits snuggly on top of the humidifier. It should alsobe noted that the humidifier is of symmetrical construction, so as toreduce the risk of malfunction, or injury to a patient, if the usershould accidentally mistake the air inlet for the air outlet and viceversa.

As shown in FIG. 2, the air outlet 6 is formed as an outlet attachment42 which is attached to a circular tube 44 which projects outwardly fromthe end wall 46 of the fourth subpassageway 26. The outlet attachment 42is provided with a tube 48 which projects through the circular tube 44and into the fourth subpassageway 26, the tube 44 being gripped betweenthe outer surface of the tube 48 and the inner surface of an outer skirtportion 49. The tube 48 extends along a portion of the length of thefourth subpassageway 26. This ensures that air can only leave the fourthsubpassageway 26 via the circular aperture 50 at the end of the tube 48,which aperture 50 is spaced away from the end wall 46.

When water waves are formed within the fourth subpassageway 26, thewaves have a particular tendency to splash against the end wall 46,resulting in the danger of water spilling into the air outlet 6. It hasbeen found that spacing the aperture 50 of the air outlet 6 away fromthe end wall 46 overcomes this problem since the water is less turbulentaway from the end wall 46. The aperture 50 should preferably be spacedat least 2 cm away from the end wall 46.

It should be appreciated that the idea of spacing the outlet aperture,in this case the aperture 50 of the tube 48, away from the walls of thehumidifier is of general applicability, and may be used in otherhumidifiers, regardless of whether the humidifiers are formed withelongate passageways.

We claim:
 1. A humidifier for producing humidified air, comprising a housing having an air inlet for receiving air to be humidified, an air outlet for discharging humidified air, and an elongate passageway extending between the air inlet and air outlet for directing air from the air inlet to the air outlet, the passageway being adapted to be partially filled with water so that air passing along the passageway becomes humidified as it passes over the water from the air inlet to the air outlet, said passageway being divided into a plurality of elongate subpassageways and at least one corner portion, each subpassageway being substantially straight, and the subpassageways being connected end to end along the length of the passageway by one or more of the corner portions and wherein said housing has a relatively low profile, being of generally flat, box-shaped construction, and includes a recess in its upper surface shaped to be of a complementary shape to an underside of a continuous positive airway pressure device adapted to be mounted thereon, wherein the passageway is provided with at least one generally U-shaped corner portion which bulges outwardly at the inside side of the corner defined by the corner portion so as to force air passing through the corner portion outwardly towards the outside side of the corner defined by the corner portion.
 2. A humidifier for producing humidified air, comprising a housing having an air inlet for receiving air to be humidified, an air outlet for discharging humidified air, and an elongate passageway extending between the air inlet and air outlet for directing air from the air inlet to the air outlet, the passageway being adapted to be partially filled with water so that air passing along the passageway becomes humidified as it passes over the water from the air inlet to the air outlet, said passageway being divided into a plurality of elongate subpassageways and at least one corner portion, each subpassageway being substantially straight, and the subpassageways being connected end to end along the length of the passageway by one or more of the corner portions and wherein said housing has a relatively low profile, being of generally flat, box-shaped construction, and includes a recess in its upper surface shaped to be of a complementary shape to an underside of a continuous positive airway pressure device adapted to be mounted thereon, including a last passageway being the last passageway through which air in the humidifier passes before reaching the air outlet, wherein the corner portion through which air passes before reaching the air outlet is the last corner portion and said last corner portion increases in width as it passes from the penultimate subpassageway to the last passageway, wherein the upper wall, or roof, of the last subpassageway rises gradually along the length of the last subpassageway, towards the air outlet, so as to allow the air outlet to be positioned at a greater height above the water within the last subpassageway.
 3. A humidifier for producing humidified air comprising a housing having an air inlet for receiving air to be humidified, an air outlet for discharging humidified air, and an elongate passageway extending between the air inlet and air outlet for directing air from the air inlet to the air outlet, the passageway being adapted to be partially filled with water so that air passing along the passageway becomes humidified as it passes over the water from the air inlet to the air outlet, said passageway being divided into a plurality of elongate subpassageways and at least one corner portion, each subpassageway being substantially straight, and the subpassageways being connected end to end along the length of the passageway by one or more of the corner portions and wherein said housing has a relatively low profile, being of generally flat, box-shaped construction, and includes a recess in its upper surface shaped to be of a complementary shape to an underside of a continuous positive airway pressure device adapted to be mounted thereon, including a last subpassageway being the last passageway through which air in the humidifier passes before reaching the air outlet, the last subpassageway including a roof or wall rising gradually along substantially the whole length of the last subpassageway towards the air outlet.
 4. A humidifier for producing humidified air, comprising a housing having an air inlet for receiving air to be humidified, an air outlet for discharging humidified air, and an elongate passageway extending between the air inlet and air outlet for directing air from the air inlet to the air outlet, the passageway being adapted to be partially filled with water so that air passing along the passageway becomes humidified as it passes over the water from the air inlet to the air outlet, said passageway being divided into a plurality of elongate subpassageways and at least one corner portion, each subpassageway being substantially straight, and the subpassageways being connected end to end along the length of the passageway by one or more of the corner portions and wherein said housing has a relatively low profile, being of generally flat, box-shaped construction, and includes a recess in its upper surface shaped to be of a complementary shape to an underside of a continuous positive airway pressure device adapted to be mounted thereon, including a first passageway being the first subpassageway through which the air in the humidifier passes after leaving the inlet, the first subpassageway including a roof or wall rising gradually along the length of the first subpassageway towards the air inlet. 